The stringent requirements of fifth-generation (5G) and beyond wireless networks in terms of spectral efficiency (SE) and energy efficiency (EE) could be achieved by relying on disruptive technologies such as intelligent reflecting surface (IRS) and massive multiple-input multiple-output (mMIMO) systems [1]}, [2]}, [3]}. In particular, IRS has been recently emerged as a revolutionary solution supporting high data rates and low energy consumption [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}. It consists of nearly passive elements, which can create favourable propagation conditions, especially against obstacles, by a smart adjustment of the elements' phase shifts on the impinging waves. Besides IRS, the mMIMO technology, which has been already deployed in 5G systems [13]}, assumes a large number of antennas at each base station (BS) by applying low-complexity linear precoding techniques. Among its benefits, we meet high directional beamforming and multiplexing gains while almost cancelling intra-cell interference in the large antenna regime due to channel orthogonality.
